Condensed Matter Physics Seminar

Bismuth selenide, regarded as the archetype topological insulator material, is in reality a good conducting metal with bulk carriers that derive from a self-doping caused by selenium vacancies. We report the synthesis of stoichiometric Bi₂Se₃ crystals that exhibit nonmetallic behavior in electrical transport down to low temperatures, providing the first indications of a truly insulating topological insulator material. I will discuss the peculiar presence of both electron- and hole-like carriers, along with the achievement of ambipolar transport in bulk Bi₂Se₃ crystals without gating techniques. In addition, new quantum transport studies of the proposed topological Kondo insulator samarium hexaboride will present our findings of a unique signature of non-trivial surface states.